JP2018091285A - Muffler for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of noise caused by exhaust gas exhausted from a muffler.SOLUTION: A muffler 40 comprises: a box type housing 41 comprising an inflow port 51a connected to an exhaust port 36 of an engine 21 and into which exhaust gas flows, and a discharge port 52a for discharging the exhaust gas that has flowed in; a concave part 56 for partitioning the inside of the housing 41 into a main chamber 65 including the inflow port 51a, and a capacity chamber 66 including the discharge port 52a; and a net-like straightening member 44 provided in the housing 41 so as to cover the discharge port 52a. The capacity of the capacity chamber 66 is smaller than the capacity of the main chamber 65. The concave part 56 comprises an opening part 56a that causes the main chamber 65 to communicate with the capacity chamber 66. The exhaust gas that has flowed into the main chamber 65 from the inflow port 51a flows into the capacity chamber 66 via the opening part 56a, reaches the exhaust port 52a, and passes through the straightening member 44.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an engine muffler.

An engine muffler mounted on a portable work machine such as a brush cutter is, for example, a box-shaped housing that has an inlet connected to an exhaust port of an engine and into which exhaust gas flows in, and an exhaust port through which the exhaust gas exhausted is discharged. Is provided. The inside of the housing is partitioned by a partition plate into a first chamber including the inflow port and a second chamber including the discharge port. The partition plate has a plurality of through holes that communicate the first chamber and the second chamber.
Such an engine muffler is disclosed in Patent Document 1.

JP 2014-181580 A

However, in the muffler disclosed in Patent Document 1, turbulent flow is generated in the housing due to exhaust gas colliding with the inner surface of the housing and the partition plate, and exhaust gas passing through the through hole of the partition plate. . Therefore, the turbulent energy of the exhaust gas discharged from the exhaust port of the muffler has been increased. Here, the turbulent energy corresponds to the magnitude of the fluctuation component of the flow velocity. Turbulent energy represents the ease of vortex generation. This vortex causes airflow noise (noise) generated when the exhaust gas discharged from the exhaust port of the muffler interferes with the housing of the muffler. Therefore, it has been desired to reduce airflow noise by reducing the turbulent energy of exhaust gas discharged from the exhaust port of the muffler.
In view of such a situation, an object of the present invention is to suppress generation of noise caused by exhaust gas discharged from a muffler.

  Therefore, an engine muffler according to the present invention includes a box-shaped housing that is connected to an exhaust port of an engine and into which exhaust gas flows in, and an exhaust port through which exhaust gas that flows in is discharged. And a net-like rectifying member provided on the housing so as to cover the discharge port. The volume of the volume chamber is smaller than the volume of the main chamber. The first partition portion has a first communication portion that communicates the main chamber and the volume chamber. The exhaust gas that has flowed into the main chamber from the inflow port flows into the volume chamber through the first communication portion, reaches the discharge port, and passes through the rectifying member.

  According to the present invention, the exhaust gas flowing into the main chamber from the inlet of the housing flows into the volume chamber through the first communicating portion, reaches the outlet of the housing, and passes through the rectifying member. Thereby, the exhaust gas can be decelerated in the volume chamber on the way from the main chamber to the housing outlet. Further, the exhaust gas decelerated in the volume chamber reaches the discharge port of the housing, and the flow can be adjusted by passing through the rectifying member. Therefore, the turbulent energy of the exhaust gas discharged from the muffler can be reduced by the deceleration and rectification of the exhaust gas, and hence the generation of noise due to the flow of the exhaust gas can be suppressed.

The perspective view of the brush cutter in 1st Embodiment of this invention. Explanatory drawing of the use state of the brush cutter in the first embodiment Sectional drawing which shows schematic structure of the engine and muffler in the said 1st Embodiment. Front view of the muffler in the first embodiment AA sectional view of FIG. BB sectional view of FIG. Exploded perspective view of the muffler in the first embodiment Front view of the muffler in the second embodiment of the present invention CC sectional view of FIG. DD sectional view of FIG. Exploded perspective view of the muffler in the second embodiment Front view of the muffler in the third embodiment of the present invention EE sectional view of FIG. FF sectional view of FIG. Front view of the partition plate in the third embodiment Exploded perspective view of muffler in the third embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view of a brush cutter according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram of the usage state of the brush cutter. In the present embodiment, a brush cutter will be described as an example of a portable working machine on which the engine muffler according to the present invention is mounted. However, the portable working machine on which the engine muffler according to the present invention is mounted. Is not limited to this.

  The brush cutter 1 has an operation rod 2 made of a long pipe. An engine module 3 as a power source is provided at the rear end of the operation rod 2. A tool mounting portion 4 as a working portion is provided at the tip of the operation rod 2. A tool is replaceably attached to the tool mounting portion 4. The tool mounting portion 4 is connected to the engine module 3 by a drive shaft built in the operation rod 2. The tool mounting portion 4 is rotationally driven by the engine module 3 (specifically, the engine 21).

  A handle 5 is attached to the center of the operating rod 2 in the longitudinal direction. An anti-vibration housing 6 is provided between the handle 5 and the engine module 3. A hanger 7 is attached to the outer periphery of the vibration-proof housing 6.

  The brush cutter 1 is used by being hung from the shoulder of the worker M by the hanger 8. The hanger 8 has a harness 9 and a metal fitting 10. The worker M wears the harness 9 on the upper body. In FIG. 2, the metal fitting 10 hangs down on the right side of the worker M. The worker M attaches the hanger 7 to the metal fitting 10 and uses the brush cutter 1 in this suspended state. The worker M can hold the handle 5 of the brush cutter 1 with both hands and move the brush cutter 1 to perform the brush cutting work.

  The engine module 3 mainly includes a cover 11 that forms an outer shell thereof, an engine 21 (see FIG. 3 described later), and a muffler 40 that are covered by the cover 11. The muffler 40 corresponds to the “engine muffler” of the present invention. The cover 11 is made of resin, for example.

  FIG. 3 is a cross-sectional view showing a schematic configuration of the engine 21 and the muffler 40. Here, FIG. 3 shows the engine 21 when the piston 25 is located near the top dead center. In the present embodiment, the upper side substantially coincides with the vertical upper side in the state where the engine 21 is used for the longest time (upright state).

  The engine 21 is an OHV (Over Head Valve) type four-stroke engine and is air-cooled. The engine 21 includes a cylinder part 22, a crankcase 23 attached to the lower part of the cylinder part 22, and an oil tank 24 provided below the crankcase 23.

  The cylinder part 22 has a cylindrical space for sliding the piston 25 in the vertical direction in FIG. In this space, the piston 25 is fitted with a gap slidable in the vertical direction in FIG.

  A crank chamber 27 is formed by the cylinder portion 22, the crankcase 23 and the piston 25. That is, the crank chamber 27 is formed by the side surface of the cylinder portion 22 and the cylindrical space on the crankcase 23 side formed by the piston 25 and the space in the crankcase 23. In the crank chamber 27, the volume of the internal space changes as the piston 25 slides.

  A cylinder head 28 is provided on the upper wall of the cylinder portion 22. A combustion chamber 29 is formed by the cylinder head 28, the cylinder portion 22, and the piston 25.

  The oil tank 24 is defined by an oil tank case, is provided separately from the crankcase 23, and stores lubricating oil.

  A check valve 30 is provided between the oil tank 24 and the crankcase 23 to allow only the oil flow from the crankcase 23 (crank chamber 27) to the oil tank 24.

  Here, as the piston 25 moves from the bottom dead center to the top dead center, the pressure in the crank chamber 27 becomes negative. Conversely, as the piston 25 moves from top dead center to bottom dead center, the pressure in the crank chamber 27 becomes positive. Therefore, when the pressure in the crank chamber 27 is positive, the check valve 30 is opened and oil flows from the crank chamber 27 to the oil tank 24. When the pressure in the crank chamber 27 is negative, the check valve 30 is closed.

  A crank 33 is rotatably supported in the crankcase 23. The crank 33 includes a crankshaft 33a serving as a rotation center, a counterweight (not shown), and the like. The piston 25 and the crank 33 are connected by a connecting rod 34. The connecting rod 34 and the piston 25 are swingably connected. The connecting rod 34 and the crank 33 are rotatably connected. With such a configuration, the piston 25 reciprocates in the cylinder portion 22.

The cylinder head 28 is provided with an intake port 35 and an exhaust port 36.
The intake port 35 communicates with a carburetor (not shown) via an insulator (not shown). An air cleaner (not shown) is provided on the upstream side of the carburetor. Here, the engine module 3 further includes the above-described insulator, carburetor, air cleaner, and fuel storage tank (not shown). Further, the above-described insulator, carburetor, and air cleaner are covered with a cover 11. The carburetor described above is a device that generates an air-fuel mixture by mixing fuel with the air that has passed through the air cleaner.

  The cylinder head 28 is provided with an intake valve 37 that opens and closes the intake port 35 and an exhaust valve 38 that opens and closes the exhaust port 36. Here, the intake valve 37 and the exhaust valve 38 open and close the combustion chamber 29.

  The muffler 40 is formed in a vertically long rectangular parallelepiped shape. In the present embodiment, the muffler 40 is directly connected to the exhaust port 36 of the engine 21 and communicates with each other.

Next, details of the muffler 40 will be described with reference to FIGS. 4 to 7 in addition to FIG. 3 described above.
FIG. 4 is a front view of the muffler 40. FIG. 5 is a cross-sectional view taken along the line AA in FIG. 6 is a cross-sectional view taken along line BB in FIG. FIG. 7 is an exploded perspective view of the muffler 40. In the following, for convenience of explanation, as shown in FIGS. Further, the side close to the engine 21 is the inflow side, and the side opposite to the side close to the engine 21 (in other words, the side far from the engine 21) is the discharge side. Here, the “upper side” in FIGS. 4 and 5 substantially coincides with the vertical upper side in the state where the engine 21 is used for the longest (upright state) as described above. In the following, for convenience of explanation, each part when the constituent elements of the muffler 40 are divided into three parts in the vertical direction in FIG. 4 will be referred to as the upper part, the central part, or the lower part of each constituent element.

The muffler 40 includes a housing 41, a guide member 42, at least one (three in this embodiment) cylindrical member 43, a net-like rectifying member 44, and an external duct 45.
The housing 41 has a substantially rectangular box shape, and includes a first container 51 and a second container 52. In the present embodiment, the first container 51 and the second container 52 are made of metal. Alternatively, the first container 51 and the second container 52 may be made of resin such as FRP (Fiber Reinforced Plastics) that can withstand high heat.

The first container 51 constitutes the inflow side of the housing 41. The first container 51 has a substantially rectangular box shape that opens on the discharge side. The first container 51 has an outer flange portion 54 that projects outward at the peripheral edge portion on the discharge side.
An inlet 51 a is provided on the upper portion of the first container 51. The inlet 51a is connected to the exhaust port 36.

  A guide member 42 is attached to the first container 51 so as to protrude from the inflow port 51a to the discharge side. The guide member 42 is made of metal or resin, and includes an arcuate guide plate 61, a pair of left and right fan-shaped side plates 62 provided on the left and right sides of the guide plate 61, and the guide member 42 as an inlet of the first container 51. And a flange portion 63 functioning as an attachment portion for attachment to 51a.

  The guide plate 61 is curved in an arc shape so as to go downward from the inlet 51a of the first container 51 toward the discharge side (that is, away from the inlet 51a). In this arc shape, the central angle is approximately 90 °.

  The side plate 62 closes the left and right openings of the guide plate 61 curved in an arc shape, and has a sector shape with a central angle of approximately 90 °. The side plate 62 may be provided with one or more through holes. In this embodiment, the guide member 42 includes the side plate 62, but the guide member 42 may not include the side plate 62.

  The second container 52 constitutes the discharge side of the housing 41. The 2nd container 52 is a substantially rectangular box shape opened on the inflow side. The second container 52 has an outer flange portion 55 projecting outward at the peripheral edge portion on the inflow side thereof.

A discharge port 52 a is formed at the center of the second container 52.
The second container 52 is formed with a deep dish-like recess 56 that is recessed from the discharge port 52a to the inflow side. An opening 56 a is formed in the lower portion of the recess 56. Here, the opening area of the discharge port 52a is larger than the opening area of the opening 56a.

  The first container 51 and the second container 52 are fixed to each other in a state where the outer flange portions 54 and 55 are in contact with each other.

At least one (three in this embodiment) bolt insertion holes 58 are formed through the first container 51. A male screw portion (not shown) of a bolt for fixing the housing 41 to the engine 21 can be inserted into the bolt insertion hole 58.
The second container 52 is formed with at least one (three in this embodiment) through-hole 59 penetratingly.

The cylindrical member 43 is disposed in the housing 41 and extends from the inflow side toward the discharge side. The cylindrical member 43 is attached to the first container 51 such that the opening at the end on the inflow side faces the bolt insertion hole 58 of the first container 51. The discharge side end of the cylindrical member 43 is connected to the through hole 59 of the second container 52.
Bolts (not shown) for fixing the housing 41 to the engine 21 can be inserted into the through holes 59 and the cylindrical member 43 of the second container 52.

  The rectifying member 44 is a sheet-shaped wire mesh and has air permeability. The rectifying member 44 has a sheet shape having a plurality of openings. The flow regulating member 44 is provided in the second container 52 so as to cover the discharge port 52 a of the second container 52. In FIG. 7, only a part of the rectangular sheet-shaped rectifying member 44 is illustrated as a net, but actually, the entire rectangular sheet-shaped rectifying member 44 is a net. Similarly, in the second and third embodiments described later, the entire sheet-like rectifying member 44 has a net shape.

  An external duct 45 made of metal or resin is attached to the outer surface of the second container 52. The external duct 45 is formed in a substantially cylindrical shape extending in the left-right direction, the right end thereof is closed, and the left end is opened. The external duct 45 has an opening on the inflow side thereof that communicates with the discharge port 52 a of the second container 52 via the rectifying member 44.

  In the present embodiment, the inside of the housing 41 is partitioned into a main chamber 65 and a volume chamber 66 by the concave portion 56 of the second container 52. The main chamber 65 includes the inflow port 51 a of the first container 51. The volume chamber 66 includes the discharge port 52 a of the second container 52. Here, the concave portion 56 of the second container 52 corresponds to the “first partition portion” of the present invention. The recess 56 is formed integrally with the housing 41 (second container 52).

The volume chamber 66 has an internal space surrounded by the recess 56 and the rectifying member 44. The volume of the volume chamber 66 is smaller than the volume of the main chamber 65.
The opening 56 a of the recess 56 of the second container 52 communicates the main chamber 65 and the volume chamber 66. Here, the opening 56a of the recess 56 of the second container 52 corresponds to the “first communication portion” of the present invention.

  Next, the flow of exhaust gas discharged from the exhaust port 36 through the muffler 40 to the outside will be described.

  The flow direction of the exhaust gas flowing into the main chamber 65 from the exhaust port 36 through the inflow port 51a of the muffler 40 is changed downward by the guide member 42 (particularly the guide plate 61) in the main chamber 65. Here, the guide member 42 (particularly the guide plate 61) realizes a function of guiding the flow of exhaust gas flowing into the main chamber 65 from the exhaust port 36 downward.

The exhaust gas that has passed through the guide member 42 is diffused and cooled in the main chamber 65, and then flows upward into the volume chamber 66 through the opening 56 a of the recess 56.
The flow direction of the exhaust gas that has flowed upward into the volume chamber 66 from the opening 56 a is changed by about 90 ° toward the discharge side in the volume chamber 66. Here, the function of the “flow direction changing portion” of the present invention is realized by the concave portion 56.

  In the present embodiment, the opening 56 a is formed in the lower portion of the recess 56, but the opening 56 a may be formed in the upper portion of the recess 56. When the opening 56 a is formed in the upper part of the recess 56, the exhaust gas diffused and cooled in the main chamber 65 flows downward into the volume chamber 66 through the opening 56 a of the recess 56. . In addition, the flow direction of the exhaust gas that has flowed downward into the volume chamber 66 from the opening 56 a is changed by about 90 ° in the volume chamber 66 toward the discharge side.

  Furthermore, the volume chamber 66 has an internal space surrounded by the concave portion 56 and the rectifying member 44, and the opening area of the discharge port 52a is larger than the opening area of the opening portion 56a. Therefore, the exhaust gas flowing into the volume chamber 66 from the opening 56a is diffused and decelerated in the volume chamber 66 and reaches the discharge port 52a. Then, the exhaust gas passes through the rectifying member 44 and the flow is adjusted, and then is discharged from the external duct 45 to the outside. Here, as shown in FIGS. 5 and 6, the flow direction G of the exhaust gas at the discharge port 52 a and the sheet surface P of the rectifying member 44 intersect each other. Particularly in the present embodiment, the flow direction G of the exhaust gas at the discharge port 52a and the sheet surface P of the rectifying member 44 are substantially orthogonal.

  In order to suppress the generation of noise due to the exhaust gas discharged from the exhaust port 52a of the muffler 40, the average flow velocity u of the exhaust gas at the exhaust port 52a is greater than 0 m / sec and not greater than 10 m / sec. Is preferable, and it is still more preferable to be in the range of 1 m / sec or more and 10 m / sec or less. The lower limit value of the average flow velocity u can be set based on the idling speed of the engine 21. Further, the upper limit value of the average flow velocity u can be set so that the rectifying function by the rectifying member 44 is sufficiently obtained.

here,
Q: Exhaust gas flow rate at the outlet 52a [m ³ / sec]
V _D : Engine 21 displacement [cc]
n: Rotational speed of engine 21 [rpm]
m: engine type (m = 1 is a 2-stroke engine, m = 2 is a 4-stroke engine)
Then, the flow rate Q is expressed by the following equation (1).

Also,
S: Effective opening area of rectifying member 44 (area of a portion through which exhaust gas passes) [m ² ]
Then, the average flow velocity u is expressed by the following formula (2) using the formula (1).

  Therefore, the above formula (2) is preferably used so that the average flow velocity u is preferably greater than 0 m / sec and not greater than 10 m / sec, and more preferably not less than 1 m / sec and not greater than 10 m / sec. 2) can be used to design the muffler 40.

In the present embodiment, the volume of the volume chamber 66 is set to 1 × 10 ³ mm ³ or more in order to suppress the generation of noise due to the exhaust gas discharged from the discharge port 52a of the muffler 40.

  The present inventor estimates the size of the vortex generated in the muffler based on the flow velocity of the exhaust gas flowing inside the muffler as disclosed in Patent Document 1 and the frequency of sound (noise) resulting from the flow. As a result, it has been found that the size of the vortex generated in the muffler is about 0.1 to 1 mm. Therefore, in order to sufficiently obtain the rectifying function by the rectifying member 44 in order to suppress the generation of noise due to the exhaust gas discharged from the exhaust port 52a of the muffler 40, the rectifying member 44 is finer than the size of the vortex. It is preferable to have a thickness. Based on the above, in the present embodiment, the wire diameter of the wire constituting the rectifying member 44 (wire mesh) is in the range of 0.05 mm or more and 0.50 mm or less, and the number of meshes of the rectifying member 44 (metal mesh) is The range was 20 mesh or more and 200 mesh or less. Here, the number of meshes is the number of meshes (number of meshes) between 25.4 mm (1 inch).

  In the present embodiment, the rectifying member 44 can function as a spark arrester for preventing sparks scattered in the exhaust gas.

  According to this embodiment, the muffler 40 is connected to the exhaust port 36 of the engine 21 and has a box-shaped housing 41 having an inflow port 51a into which exhaust gas flows and an exhaust port 52a through which the exhaust gas flows in. 41 is divided into a main chamber 65 including the inflow port 51a and a volume chamber 66 including the discharge port 52a, and a net-like rectifier provided in the housing 41 so as to cover the discharge port 52a. And a member 44. The volume of the volume chamber 66 is smaller than the volume of the main chamber 65. The first partition portion (recessed portion 56) has a first communication portion (opening portion 56a) that communicates the main chamber 65 and the volume chamber 66. The exhaust gas flowing into the main chamber 65 from the inflow port 51a flows into the volume chamber 66 through the first communication portion (opening 56a), reaches the discharge port 52a, and passes through the rectifying member 44. Therefore, the exhaust gas can be decelerated in the volume chamber 66 on the way from the main chamber 65 to the discharge port 52 a of the housing 41. Further, the exhaust gas decelerated in the volume chamber 66 reaches the discharge port 52a of the housing 41, and the flow can be adjusted by passing through the rectifying member 44. Therefore, the turbulent energy of the exhaust gas discharged from the muffler 40 can be reduced by the deceleration and rectification of the exhaust gas, and hence the generation of noise due to the flow of the exhaust gas can be suppressed.

  Further, according to the present embodiment, the flow direction G of the exhaust gas at the discharge port 52 a intersects the sheet surface P of the rectifying member 44. Thereby, when the exhaust gas passes through the rectifying member 44, the rectifying member 44 reliably rectifies the exhaust gas.

  Moreover, according to this embodiment, the volume chamber 66 is provided with the flow direction change part (recessed part 56) which changes the flow direction of the waste gas which flowed into the inside from the 1st communication part (opening part 56a). As a result, the momentum of the exhaust gas can be reduced when the flow direction of the exhaust gas in the volume chamber 66 is changed.

  Moreover, according to this embodiment, the 1st partition part (recessed part 56) is integrally formed with the housing 41 (2nd container 52). Thereby, the discharge port 52a and the recessed portion 56 can be formed substantially simultaneously when the second container 52 is formed. Therefore, the muffler 40 can be manufactured efficiently.

  According to the present embodiment, the rectifying member 44 is a wire mesh. Therefore, it is possible to rectify the exhaust gas at the discharge port 52a using an easily available general-purpose product.

  Moreover, according to this embodiment, the wire diameter of the wire which comprises the rectification | straightening member 44 (wire net | network) is in the range of 0.05 mm or more and 0.50 mm or less. Further, the number of meshes of the rectifying member 44 (metal mesh) is in the range of 20 mesh or more and 200 mesh or less. Thereby, vortices in the exhaust gas flow that may cause noise can be reduced by the rectifying member 44 (metal mesh).

  Moreover, according to this embodiment, the average flow velocity u of the exhaust gas in the discharge port 52a is 10 m / sec or less. Thereby, the rectification member 44 (wire mesh) can rectify the exhaust gas satisfactorily.

  In the present embodiment, the rectifying member 44 can function as a spark arrester for preventing sparks scattered in the exhaust gas. Therefore, the rectifying member 44 can have both an exhaust gas rectifying function and a fire dust scattering preventing function.

Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 8 is a front view of the muffler 40 ′ in the present embodiment. 9 is a cross-sectional view taken along the line CC of FIG. 10 is a cross-sectional view taken along the line DD of FIG. FIG. 11 is an exploded perspective view of the muffler 40 ′.
Differences from the first embodiment will be described.

In the present embodiment, the muffler 40 ′ further includes a partition plate 70 made of metal or resin in the muffler 40 described above.
The partition plate 70 has a substantially rectangular plate shape, and the peripheral portion of the partition plate 70 is sandwiched between the outer flange portion 54 of the first container 51 and the outer flange portion 55 of the second container 52. And fixed to the second container 52. Therefore, the inside of the main chamber 65 is partitioned into a first chamber 68 and a second chamber 69 by the partition plate 70. The first chamber 68 includes the inflow port 51 a of the first container 51. The second chamber 69 is adjacent to the volume chamber 66.

In the present embodiment, in the muffler 40 ′, the first chamber 68, the second chamber 69, and the volume chamber 66 are arranged in this order from the inflow side to the discharge side. Here, the partition plate 70 corresponds to the “second partition portion” of the present invention.
The volume of the volume chamber 66 is smaller than the volume of the first chamber 68 and smaller than the volume of the second chamber 69.

  The inlet 51a of the first container 51 is opposed to the upper part of the partition plate 70 with the guide member 42 therebetween. In other words, in a state where the guide member 42 is positioned between the inlet 51a of the first container 51 and the upper part of the partition plate 70, the inlet 51a of the first container 51 and the upper part of the partition plate 70 are mutually connected. Opposite.

  At least one (six in FIG. 11) through-hole 71 is formed in the lower part of the partition plate 70. The first chamber 68 and the second chamber 69 communicate with each other through the through hole 71. Here, the through hole 71 communicates with the first chamber 68 and the second chamber 69 in correspondence with the “second communication portion” of the present invention. The through hole 71 is positioned below the inflow port 51 a of the first container 51. The through hole 71 is positioned below the discharge port 52 a of the second container 52.

  The partition plate 70 is formed with at least one (three in FIG. 11) through-holes 72 through which the cylindrical member 43 is inserted.

  Next, the flow of exhaust gas discharged from the exhaust port 36 through the muffler 40 'to the outside will be described.

  The direction of the flow of the exhaust gas flowing into the first chamber 68 from the exhaust port 36 through the inlet 51a of the muffler 40 ′ is changed downward by the guide member 42 (particularly the guide plate 61) in the first chamber 68. .

The exhaust gas that has passed through the guide member 42 is diffused and cooled in the first chamber 68, and then flows into the second chamber 69 through the through hole 71 of the partition plate 70.
The exhaust gas flowing into the second chamber 69 is further diffused and cooled in the second chamber 69, and then flows upward into the volume chamber 66 through the opening 56 a of the recess 56. Here, the opening 56 a of the recess 56 communicates the second chamber 69 and the volume chamber 66.

  The flow direction of the exhaust gas that has flowed upward into the volume chamber 66 from the opening 56 a is changed by about 90 ° toward the discharge side in the volume chamber 66. Further, the exhaust gas diffuses in the volume chamber 66 and is decelerated to reach the discharge port 52a. Then, the exhaust gas passes through the rectifying member 44 and the flow is adjusted, and then is discharged from the external duct 45 to the outside.

  In the present embodiment, the opening 56 a is formed in the lower portion of the recess 56, but the opening 56 a may be formed in the upper portion of the recess 56. When the opening 56 a is formed in the upper part of the recess 56, the exhaust gas diffused and cooled in the second chamber 69 flows downward into the volume chamber 66 through the opening 56 a of the recess 56. To do. In addition, the flow direction of the exhaust gas that has flowed downward into the volume chamber 66 from the opening 56 a is changed by about 90 ° in the volume chamber 66 toward the discharge side.

  In particular, according to the present embodiment, the muffler 40 ′ has a second partition portion (partition plate) that partitions the main chamber 65 into a first chamber 68 including the inflow port 51 a and a second chamber 69 adjacent to the volume chamber 66. 70). The volume of the volume chamber 66 is smaller than the volume of the first chamber 68 and smaller than the volume of the second chamber 69. The second partition (partition plate 70) has a second communication part (through hole 71) that communicates the first chamber 68 and the second chamber 69. As a result, the substantial flow distance (movement distance) of the exhaust gas from the inlet 51a to the outlet 52a of the housing 41 can be made relatively longer than the muffler 40 in the first embodiment described above. The exhaust gas pressure can be efficiently reduced within 40 '. Further, in the second communication portion (through hole 71), the cross-sectional area of the path through which the exhaust gas flows changes abruptly, so the noise reduction function of the muffler itself can be improved.

Next, a third embodiment of the present invention will be described with reference to FIGS.
Fig. 12 is a front view of the muffler 40 "according to this embodiment. Fig. 13 is a cross-sectional view taken along line EE in Fig. 12. Fig. 14 is a cross-sectional view taken along line FF in Fig. 12. Fig. 15 is a partition plate. Fig. 16 is a front view of 80. Fig. 16 is an exploded perspective view of a muffler 40 ".
Differences from the second embodiment will be described.

In the present embodiment, the second container 50 does not have the concave portion 56 described above.
In the present embodiment, the muffler 40 ″ includes a partition plate 80 made of metal or resin instead of the partition plate 70 described above.
The partition plate 80 includes a main body portion 81 that is a substantially rectangular flat plate shape, and a concave portion 82 that is formed in the center portion in the lateral direction (left-right direction).

  The peripheral portion of the main body 81 of the partition plate 80 is sandwiched between the outer flange portion 54 of the first container 51 and the outer flange portion 55 of the second container 52. The container 52 is fixed. Therefore, the inside of the main chamber 65 is partitioned into a first chamber 68 and a second chamber 69 by the partition plate 80. Here, the partition plate 80 corresponds to the “second partition portion” of the present invention.

The concave portion 82 of the partition plate 80 is composed of a first concave portion 83 that constitutes the upper portion thereof, and a second concave portion 84 that constitutes the center portion in the vertical direction and the lower portion thereof.
The first concave portion 83 is opposed to the inlet 51a of the first container 51 with the guide member 42 'interposed therebetween. In other words, in the state where the guide member 42 ′ is positioned between the first concave portion 83 and the inlet 51 a of the first container 51, the inlet 51 a of the first concave portion 83 and the first container 51. Are facing each other.

  The first concave portion 83 is curved in an arc shape so as to go downward from the inflow port 51a side toward the discharge side (that is, from the inflow side toward the discharge side). Here, the first concave portion 83 has a function of receiving the exhaust gas flowing into the first chamber 68 from the inflow port 51a and guiding it downward (for example, to the second concave portion 84).

The lower end portion of the first concave portion 83 is continuous with the upper end portion of the second concave portion 84. The second concave portion 84 protrudes more to the discharge side than the first concave portion 83.
As shown in FIG. 15, the second concave portion 84 is substantially C-shaped when viewed from the front, and is in contact with the inner surface of the second container 52 at the substantially C-shaped bottom portion 85.

  Here, the second concave portion 84 corresponds to the “first partition portion” of the present invention, and the inside of the housing 41 includes a main chamber 65 (first chamber 68 and second chamber 69) including the inflow port 51a. It divides into the volume chamber 66 containing the discharge port 52a. As shown in FIGS. 13 to 16, the volume chamber 66 is formed by being surrounded by a second concave portion 84. The volume of the volume chamber 66 is smaller than the volume of the first chamber 68 and smaller than the volume of the second chamber 69.

  In the present embodiment, the communication portion 66 a is formed by the right end portion (open end portion) of the substantially C-shaped second concave portion 84 and the inner surface of the second container 52. The communication portion 66 a corresponds to the “first communication portion” of the present invention, and communicates the second chamber 69 constituting the main chamber 65 and the volume chamber 66. Here, the opening area of the discharge port 52a is larger than the opening area of the communicating portion 66a.

  A plurality (seven in FIG. 15) of through holes 86 are formed in the left side portion of the main body 81 of the partition plate 80. Here, the through hole 86 is positioned lower than the inflow port 51 a of the first container 51. In the present embodiment, the concave portion 82 (particularly, the second concave portion 84) is located between the discharge port 52a and the plurality of through holes 86 in the horizontal direction (left-right direction).

  The partition plate 80 is formed with at least one (two in FIG. 15) through-holes 87 through which the cylindrical member 43 is inserted.

  The guide member 42 ′ is made of metal or resin and is attached to the inlet 51 a of the first container 51. The guide member 42 ′ has a U-shaped cross-sectional shape with an open bottom surface, and extends from the inlet 51 a of the first container 51 toward the discharge side. The guide member 42 ′ has a function of smoothly guiding the exhaust gas flowing into the first chamber 68 from the exhaust port 36 through the inlet 51 a to the concave portion 82 of the partition plate 80.

  In the present embodiment, the concave portion 82 (particularly, the second concave portion 84) of the partition plate 80 can partially regulate the flow of the exhaust gas in the second chamber 69.

  Next, the flow of exhaust gas discharged from the exhaust port 36 through the muffler 40 ″ to the outside will be described.

  The exhaust gas flowing into the first chamber 68 from the exhaust port 36 through the inlet 51a of the muffler 40 ″ is directed downward by the concave portion 82 (particularly, the first concave portion 83) of the partition plate 80. The exhaust gas is diffused and cooled in the first chamber 68 and then flows into the left side portion of the second chamber 69 through the through hole 86 of the partition plate 80.

  The exhaust gas flowing into the left portion of the second chamber 69 flows in the second chamber 69 so as to wrap around the upper and lower portions of the concave portion 82 (particularly, the second concave portion 84) of the partition plate 80. It reaches the right part in the two chambers 69. The exhaust gas can also be diffused and cooled in the second chamber 69.

Thereafter, the exhaust gas flows leftward into the volume chamber 66 through the communication portion 66a. Here, the communication part 66 a communicates the second chamber 69 and the volume chamber 66.
The flow direction of the exhaust gas flowing into the volume chamber 66 leftward from the communication portion 66a is changed by about 90 ° in the volume chamber 66 toward the discharge side. Here, the function of the “flow direction changing portion” of the present invention is realized by the concave portion 82 (particularly, the second concave portion 84) of the partition plate 80. Further, the exhaust gas diffuses in the volume chamber 66 and is decelerated to reach the discharge port 52a. Then, the exhaust gas passes through the rectifying member 44 and the flow is adjusted, and then is discharged from the external duct 45 to the outside.

  In particular, according to the present embodiment, the first partition (second concave portion 84) is formed integrally with the second partition (partition plate 80). The first partition (second concave portion 84) divides the inside of the housing 41 into a main chamber 65 including the inflow port 51a and a volume chamber 66 including the discharge port 52a. The second partition (partition plate 80) partitions the inside of the main chamber 65 into a first chamber 68 including the inflow port 51a and a second chamber 69 adjacent to the volume chamber 66. Thereby, when the partition plate 80 is formed, the second concave portion 84 that defines the volume chamber 66 can be formed substantially simultaneously. Therefore, the muffler 40 ″ can be manufactured efficiently.

  In the present embodiment, in the second chamber 69, the exhaust gas flowing from the left part to the right part of the second chamber 69 is on the way above and below the concave part 82 (particularly, the second concave part 84) of the partition plate 80. Although an example of flowing so as to circulate is shown, the path through which the exhaust gas circulates may be at least one above and below the concave portion 82 (particularly, the second concave portion 84) of the partition plate 80. That is, in the second chamber 69, the exhaust gas flowing from the left side portion to the right side portion flows in the middle so as to wrap around above or below the concave portion 82 (particularly, the second concave portion 84) of the partition plate 80. May be.

  In the first to third embodiments described above, a brush cutter has been described as an example of a portable work machine on which the mufflers 40, 40 ′, and 40 ″ are mounted. However, the mufflers 40, 40 ′, and 40 ″ are provided. The portable work machine installed is not limited to this. For example, the mufflers 40, 40 ′, 40 ″ can be mounted on portable working machines such as a drilling machine and a concrete cutter. The mufflers 40, 40 ′, 40 ″ are backpack blowers, sprayers (sprayers). ), Can be mounted on a backpack-type work machine such as a dusting machine or a backpack-type brush cutter.

In the first to third embodiments, the engine 21 is a four-stroke engine. However, the engine 21 may be a two-stroke engine.
In the first to third embodiments, the engine 21 is an OHV engine. However, the engine 21 may be an OHC engine.
In the first to third embodiments described above, in the engine 21, the example in which the cylinder head 28 and the cylinder portion 22 are separate from each other is shown, but instead, the cylinder head and the cylinder portion are integrated. There may be.

  As can be seen from the foregoing, the foregoing embodiments are merely illustrative of the present invention, and the present invention is made by those skilled in the art within the scope of the claims in addition to those directly shown by the described embodiments. Needless to say, it includes various improvements and changes.

DESCRIPTION OF SYMBOLS 1 Brush cutter 3 Engine module 21 Engine 36 Exhaust port 40, 40 ', 40 "Muffler 41 Housing 42, 42' Guide member 43 Cylindrical member 44 Rectification member 45 External duct 51 1st container 51a Inlet port 52 2nd container 52a Discharge port 54, 55 Outer flange portion 56 Recessed portion 56a Opening portion 58 Bolt insertion hole 59 Through hole 61 Guide plate 62 Side plate 63 Flange portion 65 Main chamber 66 Volume chamber 66a Communication portion 68 First chamber 69 Second chamber 70 Partition plate 71 , 72 Through hole 80 Partition plate 81 Main body part 82 Recessed part 83 First concave part 84 Second concave part 85 Bottom part 86, 87 Through hole G Flow direction of exhaust gas P Sheet surface

Claims (11)

A box-shaped housing connected to the exhaust port of the engine and having an inflow port for exhaust gas flowing in, and an exhaust port for discharging the inflowing exhaust gas;
A first partition that divides the housing into a main chamber including the inlet and a volume chamber including the discharge port;
A net-like rectifying member provided in the housing so as to cover the discharge port;
With
The volume of the volume chamber is smaller than the volume of the main chamber,
The first partition portion has a first communication portion that communicates the main chamber and the volume chamber,
Exhaust gas that has flowed into the main chamber from the inflow port flows into the volume chamber through the first communication portion, reaches the discharge port, and passes through the rectifying member.
Engine muffler.   The engine muffler according to claim 1, wherein a flow direction of exhaust gas at the discharge port intersects a seat surface of the rectifying member.   3. The engine muffler according to claim 1, wherein the volume chamber includes a flow direction changing unit that changes a flow direction of the exhaust gas flowing into the inside from the first communication unit. A second partition that divides the main chamber into a first chamber including the inlet and a second chamber adjacent to the volume chamber;
The volume of the volume chamber is smaller than the volume of the first chamber and smaller than the volume of the second chamber,
The engine muffler according to any one of claims 1 to 3, wherein the second partition portion includes a second communication portion that communicates the first chamber and the second chamber.   The engine muffler according to claim 4, wherein the first partition is formed integrally with the second partition.   The engine muffler according to any one of claims 1 to 4, wherein the first partition portion is formed integrally with the housing.   The engine muffler according to claim 1, wherein the rectifying member is a wire mesh. The wire diameter of the wire constituting the wire mesh is in the range of 0.05 mm or more and 0.50 mm or less,
The engine muffler according to claim 7, wherein the number of meshes of the wire mesh is in a range of 20 mesh or more and 200 mesh or less.   The engine muffler according to any one of claims 1 to 8, wherein an average flow velocity of the exhaust gas at the discharge port is 10 m / sec or less.   The engine muffler according to any one of claims 1 to 9, wherein the rectifying member is capable of functioning as a spark arrester for preventing sparks from being scattered in exhaust gas.   The engine muffler according to claim 1, wherein the engine is a four-stroke engine.